Battery separator with dielectric coating

ABSTRACT

The present disclosure generally relate to separators, high performance electrochemical devices, such as, batteries and capacitors, including the aforementioned separators, and methods for fabricating the same. In one implementation, a separator for a battery is provided. The separator comprises a substrate capable of conducting ions and at least one dielectric layer capable of conducting ions. The at least one dielectric layer at least partially covers the substrate and has a thickness of 1 nanometer to 2,000 nanometers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/836,214, filed Dec. 8, 2017, which is a continuation of U.S. patentapplication Ser. No. 15/349,477, filed Nov. 11, 2016, now U.S. Pat. No.10,411,238, which is a continuation of U.S. patent application Ser. No.14/937,442, filed Nov. 10, 2015, now U.S. Pat. No. 9,508,976, whichclaims benefit of U.S. provisional patent application Ser. No.62/101,794, filed Jan. 9, 2015, and benefit of U.S. provisional patentapplication Ser. No. 62/171,313, filed Jun. 5, 2015. All of theaforementioned related patent applications are incorporated by referenceherein in their entirety.

BACKGROUND Field

Implementations of the present disclosure generally relate toseparators, high performance electrochemical devices, such as, batteriesand capacitors, including the aforementioned separators, and methods forfabricating the same.

Description of the Related Art

Fast-charging, high-capacity energy storage devices, such as capacitorsand lithium-ion (Li-ion) batteries, are used in a growing number ofapplications, including portable electronics, medical, transportation,grid-connected large energy storage, renewable energy storage, anduninterruptible power supply (UPS).

Li-ion batteries typically include an anode electrode, a cathodeelectrode, and a separator positioned between the anode electrode andthe cathode electrode. The separator is an electronic insulator, whichprovides physical and electrical separation between the cathode and theanode electrodes. The separator is typically made from micro-porouspolyethylene and polyolefin. During electrochemical reactions, i.e.,charging and discharging, Li-ions are transported through the pores inthe separator between the two electrodes via an electrolyte. Thus, highporosity is desirable to increase ionic conductivity. However, some highporosity separators are susceptible to electrical shorts when lithiumdendrites formed during cycling create shorts between the electrodes.

Currently, battery cell manufacturers purchase separators, which arethen laminated together with anode and cathode electrodes in separateprocessing steps. Other separators are typically made by wet or dryextrusion of a polymer and then stretched to produce holes (tears) inthe polymer. The separator is also one of the most expensive componentsin the Li-ion battery and accounts for over 20% of the material cost inbattery cells.

For most energy storage applications, the charge time and capacity ofenergy storage devices are important parameters. In addition, the size,weight, and/or expense of such energy storage devices can be significantlimitations. The use of currently available separators has a number ofdrawbacks. Namely, such available materials limit the minimum size ofthe electrodes constructed from such materials, suffer from electricalshorts, require complex manufacturing methods, and expensive materials.Further, current separator designs often suffer from Lithium dendritegrowth, which may lead to short-circuits.

Accordingly, there is a need in the art for faster charging, highercapacity energy storage devices with separators that are smaller,lighter, and can be more cost effectively manufactured.

SUMMARY

Implementations of the present disclosure generally relate toseparators, high performance electrochemical devices, such as, batteriesand capacitors, including the aforementioned separators, and methods forfabricating the same. In one implementation, a separator for a batteryis provided. The separator comprises a substrate capable of conductingions and at least one dielectric layer capable of conducting ions. Theat least one dielectric layer at least partially covers the substrateand has a thickness of 1 nanometer to 2,000 nanometers.

In another implementation, a battery is provided. The battery comprisesan anode containing at least one of lithium metal or lithium-alloy or amixture of lithium metal and/or lithium alloy and another material, tin,or silicon, a cathode, and a separator disposed between the anode andthe cathode. The separator comprises a porous substrate capable ofconducting ions and at least one dielectric layer capable of conductingions. The at least one dielectric layer at least partially covers thesubstrate and has a thickness of 1 nanometer to 2,000 nanometers.

In yet another implementation, a separator for a battery is provided.The separator comprises at least one porous dielectric layer having athickness of 1 nanometer to 2,000 nanometers and a microporousion-conducting polymeric substrate adhered to the at least one porousdielectric layer. In one implementation, the porous dielectric layer isa porous aluminum oxide layer. In one implementation, the porousdielectric layer is a binder-free dielectric layer. In oneimplementation, the porous dielectric layer has a thickness in the rangeof 10 nanometers to 600 nanometers. In one implementation, the porousdielectric layer has a thickness in the range of 50 nanometers to 200nanometers. In one implementation, the microporous ion-conductingpolymeric substrate has a thickness in the range of 5 microns to 50microns. In one implementation, the microporous ion-conducting polymericsubstrate has a thickness in the range of 6 microns to 25 microns. Inone implementation, the microporous ion-conducting polymeric substrateis a polyolefinic membrane. In one implementation, the polyolefinicmembrane is a polyethylene membrane. In one implementation, the aluminumoxide layer further consists of zirconium oxide, silicon oxide, orcombinations thereof.

In yet another implementation, a battery is provided. The batterycomprises an anode containing at least one of lithium metal orlithium-alloy or a mixture of lithium metal and/or lithium alloy andanother material, tin, or silicon, a cathode, and a separator. Theseparator comprises at least one porous dielectric layer having athickness of 1 nanometer to 2,000 nanometers and a microporousion-conducting polymeric substrate adhered to the at least one porousdielectric layer. In one implementation, the battery further comprisesan electrolyte in ionic communication with the anode and the cathode viathe separator. In one implementation, the battery further comprises apositive current collector contacting the cathode and a negative currentcollector contacting the anode, wherein the positive current collectorand the negative current collector are each independently comprises ofmaterials selected from aluminum (Al), copper (Cu), zinc (Zn), nickel(Ni), cobalt (Co), tin (Sn), silicon (Si), manganese (Mn), magnesium(Mg), alloys thereof, and combinations thereof.

In yet another implementation, a method of forming a separator for arechargeable lithium-ion battery is provided. The method comprisesexposing a material to be deposited on a porous ion-conducting polymersubstrate positioned in a processing region to an evaporation process,flowing a reactive gas into the processing region and reacting thereactive gas and the evaporated material to deposit a dielectric layeron at least a portion of the porous ion-conducting polymer substrate. Inone implementation, the material is selected from the group consistingof: aluminum (Al), zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum(Ta), titanium (Ti), yttrium (Y), lanthanum (La), silicon (Si), boron(B), silver (Ag), chromium (Cr), copper (Cu), indium (In), iron (Fe),magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), nickel (Ni),tin (Sn), ytterbium (Yb), lithium (Li) calcium or combinations thereof.In one implementation, the reactive gas is an oxygen-containing gasselected from the group consisting of: oxygen (O₂), ozone (O₃), oxygenradicals (O*), ionized oxygen atoms, carbon dioxide (CO₂), nitric oxide(NO_(x)), water vapor, or combinations thereof. In one implementation,the dielectric layer is aluminum oxide. In one implementation, theevaporation process is a thermal evaporation process or an electron beamevaporation process. In one implementation, the microporousion-conducting polymeric substrate is exposed to a surface modificationtreatment process to enhance the nucleation/growth conditions of themicroporous ion-conducting polymeric substrate. In one implementation,the surface modification treatment process comprises supplying atreatment gas mixture into the processing region and forming a plasmafrom the treatment gas mixture to plasma treat at least a portion of themicroporous ion-conducting polymeric substrate, wherein the treatmentgas mixture comprises an oxygen-containing gas, an inert gas, orcombinations thereof. In one implementation, the method furthercomprises exposing the microporous ion-conducting polymeric substrate toa cooling process prior to exposing the material to an evaporationprocess. In one implementation, the cooling process cools themicroporous ion-conducting polymeric substrate to a temperature between−20 degrees Celsius and 22 degrees Celsius. In one implementation, thecooling process cools the microporous ion-conducting polymeric substrateto a temperature between −10 degrees Celsius and 0 degrees Celsius. Inone implementation, the evaporation process comprises exposing thematerial to a temperature of between 1,300 degrees Celsius and 1,600degrees Celsius. In one implementation, the dielectric layer is a porousaluminum oxide layer. In one implementation, the dielectric layer is abinder-free dielectric layer. In one implementation, the dielectriclayer has a thickness in the range of 1 nanometer and 2,000 nanometers.In one implementation, the dielectric layer has a thickness in the rangeof 10 nanometers to 500 nanometers. In one implementation, themicroporous ion-conducting polymeric substrate has a thickness in therange of 5 microns to 50 microns. In one implementation, the microporousion-conducting polymeric substrate has a thickness in the range of 6microns to 25 microns. In one implementation, the microporousion-conducting polymeric substrate is a polyolefinic membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description ofthe implementations, briefly summarized above, may be had by referenceto implementations, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical implementations of this disclosure and aretherefore not to be considered limiting of its scope, for the disclosuremay admit to other equally effective implementations.

FIG. 1 illustrates a cross-sectional view of one implementation of anelectrode structure formed according to implementations describedherein;

FIG. 2 illustrates a cross-sectional view of a coated separator for alithium-ion battery according to implementations described herein;

FIG. 3 illustrates a process flow chart summarizing one implementationof a method for forming an electrode structure according toimplementations described herein;

FIG. 4 illustrates a schematic view of a web tool for forming aseparator according to implementations described herein;

FIGS. 5A-5B illustrate scanning electron microscope (SEM) images of analuminum oxide layer coated on a 25 micron polymeric separator accordingto implementations described herein;

FIG. 6 illustrates a transmission electron microscope (TEM) image of analuminum oxide layer coated on a 25 micron polymeric separator accordingto implementations described herein;

FIG. 7 illustrates a plot depicting charge transfer resistance formonolayer and tri-layer separators with dielectric coating formedaccording to implementations described herein;

FIG. 8 illustrates a plot depicting pore size distribution based onBarrett-Joyner-Halenda (BJH) analysis for a prior art separator verses aseparators with ceramic coating according to implementations describedherein; and

FIG. 9 a process flow chart summarizing another implementation of amethod for forming an electrode structure according to implementationsdescribed herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneimplementation may be beneficially incorporated in other implementationswithout further recitation. It is to be noted, however, that theappended drawings illustrate only exemplary implementations of thisdisclosure and are therefore not to be considered limiting of its scope,for the disclosure may admit to other equally effective implementations.

DETAILED DESCRIPTION

The following disclosure describes separators, high performanceelectrochemical cells and batteries including the aforementionedseparators, and methods for fabricating the same. Certain details areset forth in the following description and in FIGS. 1-9 to provide athorough understanding of various implementations of the disclosure.Other details describing well-known structures and systems oftenassociated with electrochemical cells and batteries are not set forth inthe following disclosure to avoid unnecessarily obscuring thedescription of the various implementations.

Many of the details, dimensions, angles and other features shown in theFigures are merely illustrative of particular implementations.Accordingly, other implementations can have other details, components,dimensions, angles and features without departing from the spirit orscope of the present disclosure. In addition, further implementations ofthe disclosure can be practiced without several of the details describedbelow.

Implementations described herein will be described below in reference toa high rate evaporation process that can be carried out using aroll-to-roll coating system, such as TopMet™, SmartWeb™, TopBeam™, allof which are available from Applied Materials, Inc. of Santa Clara,Calif. Other tools capable of performing high rate evaporation processesmay also be adapted to benefit from the implementations describedherein. In addition, any system enabling high rate evaporation processesdescribed herein can be used to advantage. The apparatus descriptiondescribed herein is illustrative and should not be construed orinterpreted as limiting the scope of the implementations describedherein. It should also be understood that although described as aroll-to-roll process, the implementations described herein may also beperformed on discrete polymer substrates.

The term “about” generally indicates within ±0.5%, 1%, 2%, 5%, or up to±10% of the indicated value. For example, a pore size of about 10 nmgenerally indicates in its broadest sense 10 nm±10%, which indicates9.0-11.0 nm. In addition, the term “about” can indicate either ameasurement error (i.e., by limitations in the measurement method), oralternatively, a variation or average in a physical characteristic of agroup (e.g., a population of pores).

The term “crucible” as used herein shall be understood as a unit capableof evaporating material that is fed to the crucible when the crucible isheated. In other words, a crucible is defined as a unit adapted fortransforming solid material into vapor. Within the present disclosure,the term “crucible” and “evaporation unit” are used synonymously.

The texture of the material and the porosity data on the materialsdescribed herein can be analyzed by dinitrogen adsorption and desorptionmeasurements. The specific surface area can be calculated byBrunauer-Emmett-Teller (BET) equation. The pore diameter distributionand the mean pore diameter can be calculated usingBarrett-Joyner-Halenda (BJH) method from the adsorption branch of the N₂adsorption-desorption isotherm.

The currently available generation batteries, especially Li-ionbatteries, use porous polyolefin separators, which are susceptible tothermal shrinkage at elevated temperatures and may cause short betweenpositive and negative electrodes or the corresponding currentcollectors. A ceramic coating on the separator helps to inhibit directcontact between electrodes and also helps to prevent potential dendritegrowth associated with Li metal. Current state of the art ceramiccoating is done using wet coating (e.g., slot-die techniques) of ceramicparticles dispersed in a polymeric binder to make the composite and asolvent to make the slurry. The coating thickness is typically around 3microns including randomly oriented dielectric material bound togetherby a polymer leading to a random pore structure. The existing ceramicparticle coating method has difficulty in reducing tortuosity due tothis random orientation of ceramic particles. Further, it is difficultto reduce the thickness of current ceramic coatings using current wetcoating methods. In order to compensate for the increased surface areaof finer ceramic powder particles current wet coating methods requireincreased amounts of both binder and solvent to decrease the viscosityof the slurry. Thus, the current wet coating methods suffer from severalproblems.

From a manufacturing point of view, an in-situ deposition of a ceramiccoating with a dry method is preferred from both a cost and performancepoint of view. In the present disclosure, a thin, low ionic resistanceceramic coating is formed on a polymeric microporous substrate, wherethe ceramic coating is formed by a dry method using reactive evaporationof metals or metal compounds. Further, the ceramic coating can be tunedfor desired thickness, micro/nanostructure, multilayered structure,morphology, pore structure and pore/ceramic orientation.

Compared to conventional ceramic coated separators, the reactiveevaporation techniques described herein have at least one of thefollowing advantages: (1) thinner separators result in less inactivecomponent volume fraction and a corresponding increase in energy densityand less ionic resistance across the separator; (2) the control ofcoating thickness and morphology provides less tortuous pores leading tosuperior separator performance; (3) the pore surface of the ceramicenhances the ionic conductivity of the overall electrolyte; and (4)suitably engineered ceramic coated separator shall enhance X-raydetection to determine manufacturing defects; and (5) higher voltagestability and puncture resistance properties of the separator can beachieved by nanocomposite coating control. Lithium dendrite inhibitingproperties of ceramic-coated separator are enhanced by nanosurfaceengineering to achieve homogeneous lithium metal deposition andstripping during cycling.

FIG. 1 illustrates an example Li-ion battery structure having a coatedseparator according to implementations of the present disclosure. Cell100 has a positive current collector 110, a positive electrode 120, acoated separator 130, a negative electrode 140 and a negative currentcollector 150. Note in FIG. 1 that the current collectors are shown toextend beyond the stack, although it is not necessary for the currentcollectors to extend beyond the stack, the portions extending beyond thestack may be used as tabs.

The current collectors 110, 150, on positive electrode 120 and negativeelectrode 140, respectively, can be identical or different electronicconductors. Examples of metals that the current collectors 110, 150 maybe comprised of include aluminum (Al), copper (Cu), zinc (Zn), nickel(Ni), cobalt (Co), tin (Sn), silicon (Si), manganese (Mn), magnesium(Mg), alloys thereof, and combinations thereof. In one implementation,at least one of the current collectors 110, 150 is perforated.Furthermore, current collectors may be of any form factor (e.g.,metallic foil, sheet, or plate), shape and micro/macro structure.Generally, in prismatic cells, tabs are formed of the same material asthe current collector and may be formed during fabrication of the stack,or added later. All components except current collectors 110 and 150contain lithium ion electrolytes.

The negative electrode 140 or anode may be any material compatible withthe positive electrode 120. The negative electrode 140 may have anenergy capacity greater than or equal to 372 mAh/g, preferably 700mAh/g, and most preferably 1000 mAh/g. The negative electrode 140 may beconstructed from a lithium metal foil or a lithium alloy foil (e.g.lithium aluminum alloys), or a mixture of a lithium metal and/or lithiumalloy and materials such as carbon (e.g. coke, graphite), nickel,copper, tin, indium, silicon, oxides thereof, or combinations thereof.The negative electrode 140 comprises intercalation compounds containinglithium or insertion compounds containing lithium.

The positive electrode 120 or cathode may be any material compatiblewith the anode and may include an intercalation compound, an insertioncompound, or an electrochemically active polymer. Suitable intercalationmaterials include, for example, lithium-containing metal oxides, MoS₂,FeS₂, MnO₂, TiS₂, NbSe₃, LiCoO₂, LiNiO₂, LiMnO₂, LiMn₂O₄, V₆O₁₃ andV₂O₅. Suitable polymers include, for example, polyacetylene,polypyrrole, polyaniline, and polythiopene. The positive electrode 120or cathode may be made from a layered oxide, such as lithium cobaltoxide, an olivine, such as lithium iron phosphate, or a spinel, such aslithium manganese oxide. Exemplary lithium-containing oxides may belayered, such as lithium cobalt oxide (LiCoO₂), or mixed metal oxides,such as LiNi_(x)Co_(1-2x)MnO₂, LiNiMnCoO₂, (“NMC”),LiNi_(0.5)Mn_(1.5)O₄, Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄, anddoped lithium rich layered-layered materials, wherein x is zero or anon-zero number. Exemplary phosphates may be iron olivine (LiFePO₄) andit is variants (such as LiFe_((1-x))Mg_(x)PO₄), LiMoPO₄, LiCoPO₄,LiNiPO₄, Li₃V₂(PO₄)₃, LiVOPO₄, LiMP₂O₇, or LiFe_(1.5)P₂O₇, wherein x iszero or a non-zero number. Exemplary fluorophosphates may be LiVPO₄F,LiAlPO₄F, Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂, Li₂CoPO₄F, or Li₂NiPO₄F.Exemplary silicates may be Li₂FeSiO₄, Li₂MnSiO₄, or Li₂VOSiO₄. Anexemplary non-lithium compound is Na₅V₂(PO₄)₂F₃.

In some implementations of a lithium ion cell according to the presentdisclosure, lithium is contained in atomic layers of crystal structuresof carbon graphite (LiC₆) at the negative electrode and lithiummanganese oxide (LiMnO₄) or lithium cobalt oxide (LiCoO₂) at thepositive electrode, for example, although in some implementations thenegative electrode may also include lithium absorbing materials such assilicon, tin, etc. The cell, even though shown as a planar structure,may also be formed into a cylinder by rolling the stack of layers;furthermore, other cell configurations (e.g., prismatic cells, buttoncells) may be formed.

Electrolytes infused in cell components 120, 130 and 140 can becomprised of a liquid/gel or a solid polymer and may be different ineach. In some implementations, the electrolyte primarily includes a saltand a medium (e.g., in a liquid electrolyte, the medium may be referredto as a solvent; in a gel electrolyte, the medium may be a polymermatrix). The salt may be a lithium salt. The lithium salt may include,for example, LiPF₆, LiAsF₆, LiCF₃SO₃, LiN(CF₃SO₃)₃, LiBF₆, and LiClO₄,BETTE electrolyte (commercially available from 3M Corp. of Minneapolis,Minn.) and combinations thereof. Solvents may include, for example,ethylene carbonate (EC), propylene carbonate (PC), EC/PC,2-MeTHF(2-methyltetrahydrofuran)/EC/PC, EC/DMC (dimethyl carbonate),EC/DME (dimethyl ethane), EC/DEC (diethyl carbonate), EC/EMC (ethylmethyl carbonate), EC/EMC/DMC/DEC, EC/EMC/DMC/DEC/PE, PC/DME, andDME/PC. Polymer matrices may include, for example, PVDF (polyvinylidenefluoride), PVDF:THF (PVDF:tetrahydrofuran), PVDF:CTFE (PVDF:chlorotrifluoroethylene) PAN (polyacrylonitrile), and PEO (polyethyleneoxide).

FIG. 2 illustrates a cross-sectional view of a coated separator 130 fora lithium-ion battery according to implementations described herein. Thecoated separator 130 comprises a porous (e.g., microporous) polymericsubstrate capable of conducting ions (e.g., a separator film) 131 withpores 132 and a first dielectric layer 133 a and an optional seconddielectric layer 133 b (collectively dielectric layer 133) positioned onopposite surfaces of the porous polymeric substrate 131. In someimplementations, the porous polymeric substrate itself does not need tobe ion conducting, however, once filled with electrolyte (liquid, gel,solid, combination etc.), the combination of porous substrate andelectrolyte is ion conducting. Although a first dielectric layer 133 aand a second dielectric layer 133 b are shown, it should be understoodthat in some implementations, only the first dielectric layer 133 a ispresent. The dielectric layer 133 is, at least, adapted for preventingelectronic shorting (e.g. direct or physical contact of the anode andthe cathode) and blocking dendrite growth. The porous polymericsubstrate 131 may be, at least, adapted for blocking (or shutting down)ionic conductivity (or flow) between the anode and the cathode duringthe event of thermal runaway. The dielectric layer 133 of the coatedseparator 130 should be sufficiently conductive to allow ionic flowbetween the anode and cathode, so that current, in desired quantities,may be generated by the cell. The porous polymeric substrate 131 and thedielectric layer 133 should adhere well to one another, i.e. separationshould not occur. As discussed herein, the dielectric layer 133 isformed on the porous polymeric substrate 131 using evaporationtechniques.

In one implementation, the porous polymeric substrate is a microporousion-conducting polymeric substrate. In one implementation, the porouspolymeric substrate is a multi-layer polymeric substrate. In oneimplementation, the pores 132 are micropores. In some implementations,the porous polymeric substrate 131 consists of any commerciallyavailable polymeric microporous membranes (e.g., single or multi-ply),for example, those products produced by produced by Polypore (CelgardInc., of Charlotte, N.C.), Toray Tonen (Battery separator film (BSF)),SK Energy (lithium ion battery separator (LiBS), Evonik industries(SEPARION® ceramic separator membrane), Asahi Kasei (Hipore™ polyolefinflat film membrane), DuPont (Energain®), etc. In some implementations,the porous polymeric substrate 131 has a porosity in the range of 20 to80% (e.g., in the range of 28 to 60%). In some implementations, theporous polymeric substrate 131 has an average pore size in the range of0.02 to 5 microns (e.g., 0.08 to 2 microns). In some implementations,the porous polymeric substrate 131 has a Gurley Number in the range of15 to 150 seconds (Gurley Number refers to the time it takes for 10 ccof air at 12.2 inches of water to pass through one square inch ofmembrane). In some implementations, the porous polymeric substrate 131is polyolefinic. Exemplary polyolefins include polypropylene,polyethylene, or combinations thereof.

The dielectric layer 133 comprises one or more dielectric materials. Thedielectric material may be a ceramic material. The ceramic material maybe an oxide. The dielectric material may be selected from, for example,aluminum oxide (Al₂O₃), AlO_(x), AlO_(x)N_(y), AlN (aluminum depositedin a nitrogen environment), calcium carbonate (CaCO₃), titanium dioxide(TiO₂), SiS₂, SiPO₄, silicon oxide (SiO₂), zirconium oxide (ZrO₂), MgO,TiO₂, Ta₂O₅, Nb₂O₅, LiAlO₂, BaTiO₃, BN, ion-conducting garnet,ion-conducting perovskite, ion-conducting anti-perovskites, porous glassceramic, and the like, or combinations thereof. In one implementation,the dielectric material is a material selected from the group consistingof: porous aluminum oxide, porous-ZrO₂, porous-SiO₂, porous-MgO,porous-TiO₂, porous-Ta₂O₅, porous-Nb₂O₅, porous-LiAlO₂, porous-BaTiO₃,ion-conducting garnet, anti-ion-conducting perovskites, porous glassdielectric, or combinations thereof. The dielectric layer 133 is abinder-free dielectric layer. In some implementations, the dielectriclayer 133 is a porous aluminum oxide layer.

In some implementations, the dielectric layer comprises from about 50wt. % to about 100 wt. % of aluminum oxide based on the total weight ofthe dielectric layer (e.g., from about 75 wt. % to about 100 wt. %; fromabout 85 wt. % to about 100 wt. % of aluminum oxide).

In some implementations, the dielectric material is blended with glassevaporated in an oxidizing atmosphere. For example, SiO₂ can beintroduced into Al₂O₃ to modify the physical properties (such asflexibility, fracture toughness) of the dielectric layer.

In some implementations, the dielectric layer 133 comprises a pluralityof dielectric columnar projections. The dielectric columnar shapedprojections may have a cauliflower-shape. The dielectric columnar shapedprojections may have a diameter that expands from the bottom (e.g.,where the columnar shaped projection contacts the porous substrate) ofthe columnar shaped projection to a top of the columnar shapedprojection. The dielectric columnar projections typically comprisedielectric grains. Nano-structured contours or channels are typicallyformed between the dielectric grains.

In some implementations, the plurality of dielectric columnarprojections may comprise one or more of various forms of porosities. Insome implementations, the columnar projections of the dielectric layer133 form a nano-porous structure between the columnar projections ofdielectric material. In one implementation, the nano-porous structuremay have a plurality of nano-pores that are sized to have an averagepore size or diameter less than about 10 nanometers (e.g., from about 1nanometer to about 10 nanometers; from about 3 nanometers to about 5nanometers). In another implementation, the nano-porous structure mayhave a plurality of nano-pores that are sized to have an average poresize or diameter less than about 5 nanometers. In one implementation,the nano-porous structure has a plurality of nano-pores having adiameter ranging from about 1 nanometer to about 20 nanometers (e.g.,from about 2 nanometers to about 15 nanometers; or from about 5nanometers to about 10 nanometers). The nano-porous structure yields asignificant increase in the surface area of the dielectric layer 133.The pores of the nano-porous structure can act as liquid electrolytereservoir and also provides excess surface area for ion-conductivity.Not to be bound by theory but it is believed that the electrolyteliquid/gel confined within the nano-porous structure behaves similar tosolid electrolyte.

In some implementations, the dielectric layer 133 has a porosity of atleast 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or 65% ascompared to a solid film formed from the same material and a porosity upto at least 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or70% as compared to a solid film formed from the same material.

Porosity is typically used since it is easy to estimate. However,tortuosity is the direct measure for describing a lithium diffusionpathway. Tortuosity describes the tortuous path for Li diffusion inporous media. For example, if diffusion is along a straight pathway, thetortuosity equals 1. Tortuosity is not easily measured due to thecomplex geometry in dielectric layers (i.e., irregular particle shapes,wide particle size distribution, etc.). It is believed that directengineering tortuosity, i.e., introducing “straight” pathway orchannels, is desirable. Dielectric layers formed using the evaporationprocesses disclosed herein exhibit lower tortuosity when compared withdielectric layers formed using currently know slot die techniques orother slurry deposition techniques.

The dielectric layer 133 may be a coating or a discrete layer, eitherhaving a thickness in the range of 1 nanometer to 2,000 nanometers(e.g., in the range of 10 nanometers to 600 nanometers; in the range of50 nanometers to 200 nanometers; in the range of 100 nanometers to 150nanometers). The porous polymeric substrate 131 is preferably a discretemembrane having a thickness in the range of 5 microns to 50 microns(e.g., in the range of 6 microns to 25 microns). The overall thicknessof the coated separator 130 is in the range of 5 microns to 60 microns(e.g., in the range of 6 microns to 50 microns; in the range of 12microns to 25 microns).

The coated separator can have any suitable total specific surface area.For example, in different implementations, the total specific surfacearea can be at least 5 m²/g, 10 m²/g, 20 m²/g, 30 m²/g, 40 m²/g, 50m²/g, 60 m²/g, 70 m²/g, 80 m²/g, 90 m²/g, 100 m²/g, 200 m²/g, 300 m²/g,400 m²/g, 500 m²/g, 600 m²/g, 700 m²/g, 800 m²/g, 900 m²/g, or 1000m²/g, or within a range bounded by any two of these.

The coated separator can have any suitable cumulative pore area. Forexample, in different implementations, the cumulative pore area can beat least 5 m²/g, 10 m²/g, 20 m²/g, 30 m²/g, 40 m²/g, 41 m²/g, 42 m²/g,43 m²/g, 44 m²/g, 45 m²/g, 46 m²/g, 47 m²/g, 48 m²/g, 49 m²/g, 50 m²/g,51 m²/g, 52 m²/g, 53 m²/g, 54 m²/g, 55 m²/g, 56 m²/g, 57 m²/g, 58 m²/g,59 m²/g, 60 m²/g, 61 m²/g, 62 m²/g, 63 m²/g, 64 m²/g, 65 m²/g, 66 m²/g,67 m²/g, 68 m²/g, 69 m²/g, 70 m²/g, 80 m²/g, 90 m²/g, 100 m²/g, 200m²/g, 300 m²/g, 400 m²/g, 500 m²/g, 600 m²/g, 700 m²/g, 800 m²/g, 900m²/g, or 1000 m²/g, or within a range bounded by any two of thesevalues.

The coated separator can have any suitable total pore volume. Forexample, in different implementations, the total pore volume can be atleast 0.5 cm³/g, 0.54 cm³/g, 0.55 cm³/g, 0.56 cm³/g, 0.6 cm³/g, 0.61cm³/g, 0.62 cm³/g, 0.63 cm³/g, 0.64 cm³/g, 0.65 cm³/g, 0.66 cm³/g, 0.67cm³/g, 0.68 cm³/g, 0.69 cm³/g, 0.7 cm³/g, 0.75 cm³/g, 0.8 cm³/g, 0.86cm³/g, 0.87 cm³/g, 0.9 cm³/g, 1 cm³/g, 1.1 cm³/g, 1.2 cm³/g, 1.3 cm³/g,1.4 cm³/g, 1.5 cm³/g, 1.6 cm³/g, 1.7 cm³/g, 1.8 cm³/g, 1.9 cm³/g, 2cm³/g, 2.1 cm³/g, or 2.2 cm³/g, or within a range bounded by any two ofthese values.

In one implementation, a first dielectric polymer layer 135 a and anoptional second dielectric layer 135 b (collectively 135) are formed onopposite surfaces of the dielectric layer 133 to further enhance theelectrochemical performance of the end device (e.g., battery). Thepolymer can be chosen from polymers currently used in the Li-ion batteryindustry. Examples of polymers that may be used to form the dielectricpolymer layer include, but are not limited to, polyvinylidene difluoride(PVDF), polyethylene oxide (PEO), poly-acrylonitrile (PAN),carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), andcombinations thereof. Not to be bound by theory but it is believed thatthe dielectric polymer layer can up-take Li-conducting electrolyte toform gel during device fabrication which is beneficial for forming goodsolid electrolyte interface (SEI) and also helps lower resistance. Thedielectric polymer layer 135 can be formed by dip-coating, slot-diecoating, gravure coating, or printing. The polymer can also be depositedusing Applied Materials Metacoat equipment. The dielectric polymer layermay have a thickness from about 5 nanometers to about 1 micrometers.

For separators made of polypropylene-polyethylene-polypropylene(PP-PE-PP) tri-layer, there is an option to enhance the bonding betweenPP-PE interface and also enhance thermal and mechanical stability of theseparator by depositing dielectric layers on top of PP or PE andintegrate tri-layer separator with dielectric layers between PP-PE.

FIG. 3 illustrates a process flow chart summarizing one implementationof a method 300 for forming an electrode structure such as cell 100depicted in FIG. 1, according to implementations described herein.

At block 310, the microporous ion-conducting polymeric substrate isoptionally exposed to a surface modification treatment to enhance thenucleation/growth conditions of the porous polymeric substrate 131. Insome implementations, the surface modification treatment process is aplasma treatment process (e.g., corona discharge treatment process). Thesurface modification treatment process performed at block 310 includessupplying a treatment gas mixture into a processing region. A plasma isthen formed from the treatment gas mixture to plasma treat the uppersurface of the porous polymeric substrate 131 to activate at least aportion of the porous polymeric substrate 131 into an excited state,forming a treated porous polymeric substrate 131 having a treated uppersurface which may then enhance the nucleation/growth conditions of thesubsequently deposited dielectric layer 133.

In one implementation, the treatment gas mixture includes at least oneof oxygen-containing gas, an inert gas (e.g., argon, helium), orcombinations thereof. In one implementation, the oxygen-containing gassupplied into the processing region includes at least one of oxygen(O₂), ozone (O₃), oxygen radicals (O*), ionized oxygen atoms, carbondioxide (CO₂), nitric oxide (NO_(x)), water vapor, or combinationsthereof. Other oxygen-containing gases may be used.

According to one implementation of the present disclosure involvingoxidation, a gas source supplies oxygen gas (O₂) through a mass flowcontroller to an ozonator, which converts a large fraction of the oxygento ozone gas (O₃). The resultant oxygen-based mixture of O₂ and O₃ andperhaps some oxygen radicals O* and ionized oxygen atoms or molecules isdelivered into the processing region. The oxygen-based gas reacts withinthe processing region with the surface of the porous polymeric substrate131, which has been heated to a predetermined, preferably lowtemperature. Ozone is a metastable molecule which spontaneously quicklydissociates in the reaction O₃→O₂+O*, where O* is a radical, which veryquickly reacts with whatever available material can be oxidized. Theozonator may be implemented in a number of forms including capacitivelyor inductively coupled plasma or a UV lamp source.

At these high ozone concentrations, the porous polymeric substrate 131need not be heated very much to achieve relatively high oxidation rates.The high ozone concentration also allows the ozone partial pressure tobe reduced. The high ozone fraction allows the ozone oxidation to beperformed at pressures of less than 20 Torr. It should be understoodthat the aforementioned surface modification technique is exemplary andother surface modifications techniques that achieve the desired surfacemodification may also be used. For example, in some implementations,this preparation may include exposing the separator to a coronatreatment, chemically treating it (e.g. with an oxidizing agent), oradsorbing or grafting a polyelectrolyte to the surface of the separator.Having a charged separator may be desired for a first layer ofoppositely charged material to bind to the separator.

In some implementations, the surface modification treatment process isan electron beam treatment process. An electron beam source is directedonto a surface of the microporous ion-conducting polymeric substrateprior to coating the microporous ion-conducting polymeric substrate. Theelectron beam source may be a linear source. The electron beam deviceemitting the electron beam is typically adapted such that the electronbeam affects the microporous ion-conducting polymeric substrate acrossits entire width, such that due to the longitudinal movement of themicroporous ion-conducting polymeric substrate, the whole surface (onone side) of the microporous ion-conducting polymeric substrate istreated with the electron beam. The electron beam device may for examplebe an electron source such as an electron flood gun, a linear electrongun, an electron beam, or the like. The gas used in the electron sourcemay be Argon, O₂, N₂, CO₂, or He, more particularly O₂, N₂, CO₂, or He.

The microporous ion-conducting polymeric substrate treated with theemitted electrons is physically, respectively structurally altered inorder to achieve improved adhesion between the microporousion-conducting polymeric substrate and the subsequently depositeddielectric layer. The desired effect can be achieved by providingelectrons at energies from 1 keV to 15 keV, more typically from 5 keV to10 keV, for example, 6 keV, 7 keV, 8 keV or 9 keV. Typical electroncurrents are from 20 mA to 1500 mA, for example 500 mA.

At block 320, the porous polymeric substrate 131 is optionally exposedto a cooling process. In one implementation, the porous polymericsubstrate 131 may be cooled to a temperature between −20 degrees Celsiusand room temperature (i.e., 20 to 22 degrees Celsius) (e.g., −10 degreesCelsius and 0 degrees Celsius). In some implementations, the porouspolymeric substrate 131 may be cooled by cooling the drum that themicroporous ion-conducting polymeric substrate travels over. Otheractive cooling means may be used to cool the microporous ion-conductingpolymeric substrate. During the evaporation process, the porouspolymeric substrate 131 may be exposed to temperatures in excess of1,000 degrees Celsius thus it is beneficial to cool the porous polymericsubstrate 131 prior to the evaporation process of block 330.

At block 330, the material to be deposited on the porous polymericsubstrate 131 is exposed to an evaporation process to evaporate thematerial to be deposited in a processing region. The evaporationmaterial may be chosen from the group consisting of aluminum (Al),zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum (Ta), titanium(Ti), yttrium (Y), lanthanum (La), silicon (Si), boron (B), silver (Ag),chromium (Cr), copper (Cu), indium (In), iron (Fe), magnesium (Mg),calcium (Ca), strontium (Sr), barium (Ba), nickel (Ni), tin (Sn),ytterbium (Yb), lithium (Li), calcium (Ca) or combinations thereof.Typically, the material to be deposited is a metal such as aluminum.Further, the evaporation material may also be an alloy of two or moremetals. The evaporation material is the material that is evaporatedduring the evaporation and with which the microporous ion-conductingpolymeric substrate is coated. The material to be deposited (e.g.,aluminum) can be provided in a crucible. The aluminum can, for example,be evaporated by thermal evaporation techniques or by electron beamevaporation techniques.

In some implementations, the evaporation material is fed to the crucibleas a wire. In this case, the feeding rates and/or the wire diametershave to be chosen such that the desired ratio of the evaporationmaterial and the reactive gas is achieved. In some implementations, thediameter of the feeding wire for feeding to the crucible is chosenbetween 0.5 mm and 2.0 mm (e.g., between 1.0 mm and 1.5 mm). Thesedimensions may refer to several feedings wires made of the evaporationmaterial. Typical feeding rates of the wire are in the range of between50 cm/min and 150 cm/min (e.g., between 70 cm/min and 100 cm/min).

The crucible is heated in order to generate a vapor, which reacts withthe reactive gas supplied at block 340 to coat the porous polymericsubstrate 131 with the dielectric layer 133. Typically, the crucible isheated by applying a voltage to the electrodes of the crucible, whichare positioned at opposite sides of the crucible. Generally, accordingto implementations described herein, the material of the crucible isconductive. Typically, the material used as crucible material istemperature resistant to the temperatures used for melting andevaporating. Typically, the crucible of the present disclosure is madeof one or more materials selected from the group consisting of metallicboride, metallic nitride, metallic carbide, non-metallic boride,non-metallic nitride, non-metallic carbide, nitrides, titanium nitride,borides, graphite, TiB₂, BN, B₄C, and SiC.

The material to be deposited is melted and evaporated by heating theevaporation crucible. Heating can be conducted by providing a powersource (not shown) connected to the first electrical connection and thesecond electrical connection of the crucible. For instance, theseelectrical connections may be electrodes made of copper or an alloythereof. Thereby, heating is conducted by the current flowing throughthe body of the crucible. According to other implementations, heatingmay also be conducted by an irradiation heater of an evaporationapparatus or an inductive heating unit of an evaporation apparatus.

The evaporation unit according to the present disclosure is typicallyheatable to a temperature of between 1,300 degrees Celsius and 1,600degrees Celsius, such as 1,560 degrees Celsius. This is done byadjusting the current through the crucible accordingly, or by adjustingthe irradiation accordingly. Typically, the crucible material is chosensuch that its stability is not negatively affected by temperatures ofthat range. Typically, the speed of the porous polymeric substrate 131is in the range of between 20 cm/min and 200 cm/min, more typicallybetween 80 cm/min and 120 cm/min such as 100 cm/min. In these cases, themeans for transporting should be capable of transporting the substrateat those speeds.

At block 340, a reactive gas is flowed into the processing region forreacting with the evaporated material to form a dielectric layer on atleast a portion of the porous polymeric substrate. According to typicalimplementations, which can be combined with other implementationsdescribed herein, the reactive gases can be selected from the groupconsisting of: oxygen-containing gases, nitrogen-containing gases, orcombinations thereof. Exemplary oxygen-containing gases that may be usedwith the implementations described herein include oxygen (O₂), ozone(O₃), oxygen radicals (O*), or combinations thereof. Exemplary nitrogencontaining gases that may be used with the implementations describedherein include N₂, N₂O, NO₂, NH₃, or combinations thereof. According toyet further implementations, additional gases, typically inert gasessuch as argon can be added to a gas mixture comprising the reactive gas.Thereby, typically the amount of reactive gas can be more easilycontrolled. According to typical implementations, which can be combinedwith other implementations described herein, the process can be carriedout in a vacuum environment with a typical atmosphere of 1*10⁻² mbar to1*10⁻⁶ mbar (e.g., 1*10⁻³ mbar or below; 1*10⁻⁴ mbar or below).

At block 350, an optional post-deposition treatment of the depositeddielectric layer is performed. The optional post-deposition treatmentmay include a post-deposition plasma treatment to densify the depositeddielectric layer, additional “functionalization” processes may beperformed post-deposition; for example, complete oxidation of AlO_(x) toform Al₂O₃, or deposition of polymer material to enhance punctureresistance of the membrane etc.

Deposition continues until the desired thickness of the dielectric layeris deposited and the coated separator is removed from the web tool 400.It should be noted that the deposition can be repeated for forming filmson both sides of the separator structure.

Optionally, at block 360, a dielectric polymer layer is deposited on thedielectric layer. The dielectric polymer layer can be formed bydip-coating, slot-die coating, gravure coating, or printing.

According to some implementations, the separator of FIG. 2 may befabricated utilizing the following processes and equipment. Oneconfiguration of a web tool for fabricating separators according to thepresent disclosure are shown schematically in FIG. 4—it should be notedthat this is a schematic representation and it is understood thatconfiguration of the web system and modules may be varied as needed tocontrol the different processes of the fabrication processes.

A dielectric coated separator may be fabricated using tools of thepresent disclosure as described herein. According to someimplementations, a web tool for forming dielectric coated separators maycomprise: a reel to reel system for taking a separator through thefollowing modules: a module for depositing a thin film of dielectricmaterial on the separator; wherein the module for depositing the thinfilm of dielectric material may include an evaporation system, such asan electron-beam evaporator or a thermal evaporator, and a thin filmtransfer system (including large area pattern printing systems such asgravure printing systems). In some implementations, the tool may furthercomprise a module for surface modification, such as a plasmapretreatment module, of the separator prior to deposition of thedielectric layer. In some implementations, the tool may further comprisea module for cooling the separator prior to deposition of the dielectriclayer. In some implementations, the tool may further comprise a modulefor plasma treatment of the dielectric layer. In some implementations,the tool may further comprise a module for forming a protective coatingover the dielectric layer. Furthermore, in some implementations the toolmay further comprise a module for depositing a lithium ion-conductingpolymer, a binder soluble in a liquid electrolyte, or a lithiumion-conducting dielectric material into the pores of the separator.

In FIG. 4, the web tool 400 may comprise: reels 412 and 414 for moving acontinuous sheet of separator material 410 through the differentprocessing modules; a module 420 for surface modification of the surfaceof the separator material 410, a module 430 for cooling the separatormaterial 410, an evaporation module 440 for depositing a dielectriclayer on at least one surface of the separator material 410; and amodule 450 for forming a protective coating over the dielectric layer.The area 460 indicates a portion of the web tool that may need to beunder a controlled environment—for example a nitrogen gas environment.In some implementations, the finished separator will not be collected onreel 414 as shown in the figures, but may go directly for integrationwith the positive and negative electrodes, etc., to form battery cells.

The evaporation module 440 has a processing region 444 that is shown tocomprise an evaporation source 442 that may be placed in a crucible,which may be a thermal evaporator or an electron beam evaporator (cold)in a vacuum environment, for example. A gas source 470 for supplyingreactive gas to the processing region 444 is coupled with the processingregion 444.

Additional modules may be included. In some implementations, additionalmodules may provide for deposition of an electrolyte soluble binder forfilling the pores of the separator in order to avoid accumulation ofdielectrics in the pores during deposition, or in some implementations,additional modules may provide for deposition of a lithiumion-conducting polymer for filling the pores of the separator.

The dielectric layer effectively reduces or eliminates battery cellfailures due to thermal shrinkage and associated tearing of separatorssuch as the polyolefin separators. Deposition of the dielectric layer inevaporation module 440 may proceed as described in FIG. 3.

The deposition processes of module 430 may include: for barrier layerdeposition a thermal spray, PVD deposition (such as cold electron beam,sputter, etc.), etc.; and for polymer (binder or lithium ion-conductingmaterial) deposition a thermal spray, slot die, etc.

The protective coating formation process of module 450 may include: fora lithium carbonate coating controlled exposure to carbon dioxide (toprovide a specific carbonate thickness); for an inorganic protectivecoating a thermal spray process, PVD deposition process (such as coldelectron beam, sputter, etc.), etc.; and for a polymer coating a thermalspray process, slot die process, etc.

A Li-ion battery with a separator according to implementations of thepresent disclosure may be combined with positive and negative electrodesto form a battery such as schematically shown in FIG. 1. The integrationof the separator with the other battery components may occur in the samemanufacturing facility used for fabricating the separator, or theseparator may be shipped on a spool and integration may occur elsewhere.The process of fabricating a battery proceeds generally as follows:separator, negative electrode and positive electrode are provided; theseparator, negative electrode and positive electrode are individuallycut into sheets of the desired size for a cell; tabs are added to thecut sheets of positive and negative electrodes; the cut sheets ofpositive and negative electrodes and separators are combined to formbattery cells; battery cells may be wound or stacked to form the desiredbattery cell configuration; after the winding or stacking, the batterycells are placed in cans, the cans are evacuated, filled withelectrolyte and then sealed.

Although implementations of the present disclosure have beenparticularly described with reference to lithium ion batteries withgraphitic negative electrodes, the teaching and principles of thepresent disclosure may be applicable to other lithium-based batteriessuch as Li-polymer, Li—S, Li—FeS₂, Li metal based batteries, etc. Forthe Li metal-based batteries such as Li—S and Li—FeS₂ a thicker Li metalelectrode may be needed and the thickness of Li metal depends on thepositive electrode loading. In some implementations the Li metalelectrode may be between 3 and 30 microns thick for Li—S and roughly190-200 microns for Li—FeS₂, and may be deposited on one or both sidesof a compatible substrate such as a Cu or stainless steel metal foil—themethods and tools described herein may be used to fabricate such Limetal electrodes.

Furthermore, in some implementations a thin (sufficient to compensatefor the irreversible loss of lithium metal during the first batterycycle) film of dielectric layer may be deposited directly on thenegative electrode using the methods and tools of the presentdisclosure—for example, a thin film of lithium metal may be deposited ona graphitic (with or without silicon) layer on a suitable electricallyconductive substrate (for example copper, etc.).

The foregoing separator, while primarily designed for use in high-energyrechargeable lithium batteries, may be used in other battery systems inwhich dendrite growth may be a problem.

EXAMPLES

The following non-limiting examples are provided to further illustrateimplementations described herein. However, the examples are not intendedto be all-inclusive and are not intended to limit the scope of theimplementations described herein.

The following examples were performed on a vacuum web coating toolhaving a metal evaporation source, an electron beam source, a microwaveplasma generator, a quartz thickness monitor, having a maximum filmspeed of 10 meters/minute, a film width of 280 millimeters and a filmlength of approximately 1 kilometer.

Table I depicts the process conditions for various dielectric filmsformed according to the implementations described herein.

TABLE I 20 μm single 20 μm trilayer 16 μm trilayer film film filmprogrammed nm 45 (single 135/180 (dual 45 AlO_(x) thickness pass) speedmulti pass) coating drum ° C. −20  −20  −20  temperature web tension N80 80 80 base pressure mbar  <10⁻⁴  <10⁻⁴  <10⁻⁴ process pressure mbar1 * 10⁻² and 1.5 * 10⁻² 1.5 * 10⁻² 2 * 10⁻² total Oxygen flow sccm10100   9200  9000  diffuse Argon sccm 0 and 1500 1000  1000  flowpretreatment W 500  500  300  power

FIGS. 5A-5B illustrates a SEM image of an approximately 100 nanometeraluminum oxide layer coated on a 25 micron polymeric separator accordingto implementations described herein. The columnar structure of thealuminum oxide dielectric layer is visible in FIG. 5B. Adhesion betweenthe polyolefinic layer and the aluminum oxide layer is also visible.

FIG. 6 illustrates a TEM image of an approximately 100 nanometer coatedon a 25 micron polymeric separator according to implementationsdescribed herein. The columnar structure and channels formed between thecolumns of aluminum oxide are also visible in FIG. 6.

FIG. 7 illustrates a plot 700 depicting charge-transfer resistance(R_(CT)) for monolayer and tri-layer separators with dielectric coatingformed according to implementations described herein. The y-axisrepresents charge-transfer resistance (R_(CT)). The x-axis representsthe thickness of the aluminum oxide layer (35 nanometers, 147nanometers, and 172 nanometers) formed on both monolayer and tri-layerseparators. A control without any aluminum oxide coating was also used.Monolayer separators were used for the 35 nanometer and control.Tri-layer separators were used for the 147 nanometer and 172 nanometerexamples. As depicted in FIG. 7, the R_(CT) for all three of thedielectric coated separators is lower than the R_(CT) for the uncoatedseparator.

Impedance spectra analysis of coin cells is depicted in Table II.

TABLE II Li/2 separator_1M LiPF₆ in EC:EMC 1:3, ~35 nm 147 nm 500 nm 2%VC/Li coin cell Control AlO_(x) AlOx_(x) AlO_(x) Room Temperature 3.30 ×10⁻³ 1.78 × 10⁻³ 14.3 × 10⁻³ 13.0 × Ionic Conductivity 10⁻³ (S/cm)Charge Transfer 417.4 190.6 67.3 46.6 Resistance (Ohm_cm²)

Thermal shrinkage results are depicted in Table III and Table IV. WD isthe web direction and TD is the transverse direction. The thermalshrinkage test was performed using 2×2 cm square cut-outs of separatormaterial with a dielectric coating deposited according to theimplementations described herein. Exemplary separator materials includeCelgard® PP2075 (20 um microporous monolayer PP membrane), Celgard®PP1615 (16 um microporous monolayer polyethylene membrane), Celgard®2320 (20 um microporous trilayer membrane (PP/PE/PP)), and Celgard® C210(16 um microporous trilayer membrane (PP/PE/PP)). As depicted in TableIII, there was no visible thermal shrinkage with either a 120 nanometerdielectric coating or a 200 nanometer dielectric coating.

TABLE III Di- electric 135° C./ 135° C./ Coating Pris- 30 minutes 60minutes Thick- tine Shrink- Shrink- Sample ness Direction cm cm age % cmage % 1. 120 nm WD 2 2 0% 2 0% TD 2 2 0% 2 0% 2. 200 nm WD 2 2 0% 2 0%TD 2 2 0% 2 0%

As depicted in Table IV, there was no visible thermal shrinkage witheither a 120 nanometer dielectric coating or a 200 nanometer dielectriccoating at exposure to temperature of 165 degrees Celsius for 60 minuteswith the application of pressure. However, thermal shrinkage was visibleat exposure to a temperature of 165 degrees Celsius for 60 minuteswithout the application of pressure.

TABLE IV 165° C./ 165° C./ 60 minutes Coating Pris- 30 minutes withpressure Sam- Thick- Direc- tine Shrink- Shrink- ple ness tion cm cm age% cm age % 1. 120 nm WD 2 1.95  −2.5% 2 0% TD 2 2      0% 2 0% 2. 200 nmWD 2 1.6 −20.0% 2 0% TD 2 2      0% 2 0%

Results achieved include: (1) Uniform 30 nm and 175 nm thick AlOxcoating was completed using Al evaporation in reactive oxygenenvironment on porous polyolefin separator of 40 cm wide, 400-800 meterslong web, (thickness 16 um, 20 um and 25 um) with corona surfacetreatment (2) The AlO_(x) coating adhesion seems to be good with scotchtape peeling tests (3) the wettability of AlO_(x) coated separator isbetter than uncoated separator (4) the Li symmetric cells showed 2×reduction in charge transfer resistance compared to control indicatingthat dielectric coating pores offer least resistance and (5) SEM crosssection image showed columnar AlO_(x) structure and crystallites arealigned vertically on the porous separator substrate.

Table V and Table VI depict the Brunauer-Emmett-Teller (BET) SurfaceArea Analysis and Barrett-Joyner-Halenda (BJH) Pore Size and VolumeAnalysis determined using test method ISO 15901-2:2006 for a Celgard®PP1615 separator having a thickness of 16 μm. BET analysis providessurface area evaluation of materials by nitrogen multilayer adsorptionmeasured as a function of relative pressure using a fully automatedanalyzer. BET techniques encompass external area and pore areaevaluations to determine the total specific surface area in m²/gyielding information about surface porosity. BJH techniques are alsoemployed to determine pore area and pore volume with 4V/A pore diameterusing adsorption and desorption techniques.

The results are depicted for an uncoated Celgard® PP1615 separator, aCelgard® PP1615 separator coated on one surface with an AlOx layeraccording to implementations described herein, and a Celgard® PP1615separator coated with an AlOx layer on opposing sides according toimplementations described herein. Column 1 of Table VI is deduced fromthe adsorption part of the isotherm and column 2 of Table VI is deducedfrom the desorption part of the isotherm. The results depicted in TableV and Table VI demonstrate that the base material structure (e.g. theporous poly-olefin layer) is not altered by the ceramic coating process.

TABLE V BET Total BJH Adsorption Specific Cumulative BJH DesorptionSurface Area Area of cumulative surface Material (m²/g) Pores m²/g areaof pores m²/g Celgard ®- 40.17 46.41 62.11 PP1615_16 μm AlOx_1-side-34.89 41.01 56.68 coated_PP1615 AlOx_2-side- 36.70 43.56 58.68coated_PP1615

TABLE VI Pore Volume Pore Volume Between 17 Å Between 17 Å BJHAdsorption BJH Desorption and 3,000 Å and 3,000 Å Average Pore Averagewidth (cm³/g) width (cm³/g) Width (4 V/A) Pore Width Material(Adsorption) (Desorption) (Å) (4 V/A) (Å) Celgard ®- 0.7175 0.7519618.42 484.28 PP1615_16 μm AlOx_1-side- 0.6339 0.6443 618.32 454.68coated_PP1615 AlOx_2-side- 0.6610 0.6635 720.22 606.97 coated_PP1615

FIG. 8 illustrates a plot 800 depicting pore size distribution based onBarrett-Joyner-Halenda analysis for a prior art separator verses aseparator with ceramic coating according to implementations describedherein. The pore size distribution is shown for an uncoated Celgard®PP1615 separator having a thickness of 16 μm, a Celgard® PP1615separator having a thickness of 16 μm and coated on one surface with a˜250 nm AlOx coating according to implementations described herein, anda Celgard® PP1615 separator having a thickness of 16 μm and coated ontwo opposing surfaces with a ˜200 nm AlOx coating according toimplementations described herein.

In some implementations, the substrate has a plurality of pores and theat least one dielectric layer does not block a majority of the pores. Insome implementations, the substrate has a plurality of pores and the atleast one dielectric layer does not block 60% or more of the pores. Forexample, in different implementations, the at least one dielectric layerdoes not block at least 50% or more, 55% or more, 60% or more, 65% ormore, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more,or within a range bounded by any two of these values.

Table VII depicts an estimate of the unblocked pores for implementationsof the present disclosure. The control substrates labeled as “Control”in the first column are uncoated separators. The second and thirdcolumns represent the width and length of the substrate/separator. Thefourth column represents the mass of the substrate for the substrateslabeled (Control) and the total mass of the substrate and the dielectriccoating for the substrates coated according to the present disclosure.The percent of estimated pore unblocked in column 7 is based on the porevolume for the control versus a single layer dielectric coated sample.

TABLE VII BET Adsorption Estimated Desorption Desorption SubstrateSurface Pore pore Average Total Pore Thickness, Width, Length, Mass,Area, Volume, unblocked Pore Volume, (μm) (cm) (cm) (g) (m²/g) (cm³/g)(%) Width, (Å) (cm³/g) 20 5 18 0.089 65.28 0.945 100.000 579.02 0.084(Control) 20 5 18 0.095 64.07 0.907 96.016 566.45 0.086 20 5 18 0.09266.84 0.950 100.562 568.68 0.087 16 5 18 0.067 40.17 0.737 100.000733.43 0.049 (Control) 16 5 18 0.085 36.71 0.661 89.725 720.22 0.056 165 18 0.084 34.90 0.640 86.832 733.06 0.054 25 5 18 0.116 48.64 0.612100.000 503.26 0.071 (Control) 25 5 18 0.135 44.35 0.508 83.013 458.170.069

FIG. 9 a process flow chart summarizing another implementation of amethod 900 for forming an electrode structure according toimplementations described herein. The method 900 may be used, forexample, to form the coated separator 130 depicted in FIG. 2. The method900 is similar to the method 300 discussed above except that thedielectric material is formed directly on the surface of the anode, thesurface of the cathode, or both the surface of the anode and the surfaceof the cathode.

At block 910, the material to be deposited on the surface of thepositive electrode is evaporated. The evaporation process of block 910may be performed similarly to the evaporation process of block 330 ofmethod 300.

At block 920, a reactive gas is flowed into the processing region forreacting with the evaporated material to deposit dielectric material onat least a portion of a surface of the positive electrode. The processof block 920 may be performed similarly to the evaporation process ofblock 340 of method 300.

At block 930, the material to be deposited on the surface of thepositive electrode is evaporated. The evaporation process of block 930may be performed similarly to the evaporation process of block 330 ofmethod 300.

At block 940, a reactive gas is flowed into the processing region forreacting with the evaporated material to deposit dielectric material onat least a portion of a surface of the negative electrode. The processof block 940 may be performed similarly to the evaporation process ofblock 340 of method 300.

At block 950, a dielectric polymer layer may be formed on the dielectriclayer. The process of block 950 may be performed similarly to theprocess of block 360 of method 300.

At block 960, the positive electrode and the negative electrode arejoined together with the dielectric material and a microporous ionconducting polymer substrate positioned therebetween. In implementationswhere dielectric material is formed on both the surface of the anode andthe surface of the cathode, the electrode structure has a coatedseparator with a dielectric coating on opposing sides. Inimplementations where dielectric material is only deposited on eitherthe surface of the anode or the surface of the cathode, the electrodestructure has a separator with only one side coated with dielectricmaterial.

While the foregoing is directed to implementations of the presentdisclosure, other and further implementations of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1. A method of forming an anode structure, comprising: exposing a material to be deposited on an anode structure positioned in a processing region to an evaporation process; flowing a reactive gas into the processing region; and reacting the reactive gas and the evaporated material to deposit a porous dielectric layer on at least a portion of the anode structure.
 2. The method of claim 1, wherein the material is selected from the group consisting of: aluminum (Al), zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum (Ta), titanium (Ti), yttrium (Y), lanthanum (La), silicon (Si), boron (B), silver (Ag), chromium (Cr), copper (Cu), indium (In), iron (Fe), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), nickel (Ni), tin (Sn), ytterbium (Yb), lithium (Li), calcium (Ca) and combinations thereof.
 3. The method of claim 1, wherein the reactive gas is an oxygen-containing gas selected from the group consisting of: oxygen (O₂), ozone (O₃), oxygen radicals (O*), ionized oxygen atoms, carbon dioxide (CO₂), nitric oxide (NO_(x)), water vapor, and combinations thereof.
 4. The method of claim 1, wherein the dielectric layer is a porous aluminum oxide.
 5. The method of claim 4, wherein the porous aluminum oxide further comprises zirconium oxide, silicon oxide, or combinations thereof.
 6. The method of claim 1, wherein the evaporation process is a thermal evaporation process or an electron beam evaporation process.
 7. The method of claim 1, wherein the anode structure is exposed to a surface modification treatment process to enhance nucleation conditions of the electrode structure.
 8. The method of claim 7, wherein the surface modification treatment process comprises: supplying a treatment gas mixture into the processing region; and forming a plasma from the treatment gas mixture to plasma treat at least a portion of the anode structure, wherein the treatment gas mixture comprises an oxygen-containing gas, an inert gas, or combinations thereof.
 9. The method of claim 1, further comprising: exposing the anode structure to a cooling process prior to exposing the material to the evaporation process.
 10. The method of claim 9, wherein the cooling process cools the anode structure to a temperature between −20 degrees Celsius and 22 degrees Celsius.
 11. The method of claim 1, further comprising forming a dielectric polymer layer on the porous dielectric layer.
 12. The method of claim 1, wherein the anode contains at least one of lithium metal, lithium-alloy, or a mixture of lithium metal and lithium alloy.
 13. The method of claim 12, wherein the anode further contains materials selected from the group consisting of: carbon, nickel, copper, tin, indium, silicon, and combinations thereof.
 14. An anode electrode structure, comprising: an anode containing at least one of lithium metal, lithium-alloy, or a mixture of lithium metal and lithium alloy; and at least one dielectric layer capable of conducting ions, wherein the at least one dielectric layer at least partially covers a surface of the anode and has a thickness of 1 nanometer to 2,000 nanometers.
 15. The anode electrode structure of claim 14, wherein the dielectric layer is a material selected from the group of: porous boron nitride, aluminum oxide, porous-ZrO₂, porous-SiO₂, porous-MgO, porous-TiO₂, porous-Ta₂O₅, porous-Nb₂O₅, porous-LiAlO₂, porous-BaTiO₃, ion-conducting garnet, ion-conducting perovskites, ion-conducting anti-perovskites, porous glass dielectric, or combinations thereof.
 16. The anode electrode structure of claim 14, wherein the dielectric layer is a binder-free dielectric layer.
 17. The anode electrode structure of claim 14, wherein the dielectric layer has a thickness in a range of 10 nanometers to 600 nanometers.
 18. The anode electrode structure of claim 14, wherein the dielectric layer has a thickness in a range of 50 nanometers to 200 nanometers.
 19. The anode electrode structure of claim 14, wherein the dielectric layer is a porous aluminum oxide.
 20. The anode electrode structure of claim 14, wherein the anode further contains materials selected from the group consisting of: carbon, nickel, copper, tin, indium, silicon, and combinations thereof. 